/**
 * 二次封装属于我们自己的数组
 *
 * @author jspankai@vip.qq.com
 * @date 2021/4/29 0:30
 * @className Array
 */
public class Array<E> {
    private E[] data;
    private int size;

    // 构造函数，传入数组的容量capacity构造Array
    public Array(int capacity) {
        data = (E[]) new Object[capacity];
        size = 0;
    }

    // 无参数的构造函数，默认数组的容量capacity=10
    public Array() {
        this(10);
    }

    // 获取数组中元素个数
    public int getSize() {
        return size;
    }

    public int getCapacity() {
        return data.length;
    }

    // 返回数组是否为空
    public boolean isEmpty() {
        return size == 0;
    }

    // 向所有元素后添加一个新元素 O(1)
    public void addLast(E e) {
//        if (size == data.length)
//            throw new IllegalArgumentException("AddLast failed.Array is full.");
//        data[size] = e;
//        size++;
        add(size, e);
    }

    // 向所有元素前添加一个新元素 O(n)
    public void addFirst(E e) {
        add(0, e);
    }

    // 在第index个位置插入一个新元素e O(n/2) = O(n)
    public void add(int index, E e) {
        if (size == data.length)
            resize(2 * data.length);
        if (index < 0 || index > size)
            throw new IllegalArgumentException("Add failed.Array is full.");
        for (int i = size - 1; i >= index; i--)
            data[i + 1] = data[i];

        data[index] = e;
        size++;
    }

    private void resize(int newCapacity) {
        E[] newData = (E[]) new Object[newCapacity];
        for (int i = 0; i < size; i++)
            newData[i] = data[i];
        data = newData;
    }

    // 获取index索引位置的元素 O(1)
    E get(int index) {
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Get failed. Index is illegal.");
        return data[index];
    }

    // 修改index索引位置的元素为e O(1)
    void set(int index, E e) {
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Get failed. Index is illegal.");
        data[index] = e;
    }

    // 查找数组中是否有元素e O(n)
    public boolean contains(E e) {
        for (int i = 0; i < size; i++) {
            if (data[i].equals(e))
                return true;
        }
        return false;
    }

    // 查找数组中元素e所在的索引，如果不存在元素e，则返回-1 O(n)
    public int find(E e) {
        for (int i = 0; i < size; i++) {
            if (data[i].equals(e))
                return i;
        }
        return -1;
    }

    // 从数组中删除index位置的元素，返回删除的元素 O(n)
    public E remove(int index) {
        if (index < 0 || index >= size)
            throw new IllegalArgumentException("Remove failed. Index is illegal.");

        E ret = data[index];
        for (int i = index + 1; i < size; i++)
            data[i - 1] = data[i];
        size--;
        data[size] = null;  // loitering objects != memory leak

        if (size == data.length / 2)
            resize(data.length / 2);
        return ret;
    }

    // 从数组中删除第一个元素，返回删除的元素 O(n)
    public E removeFirst() {
        return remove(0);
    }

    // 从数组中删除最后一个元素，返回删除的元素 O(1)
    public E removeLast() {
        return remove(size - 1);
    }

    // 从数组中删除元素e
    public void removeElement(E e) {
        int index = find(e);
        if (index != -1)
            remove(index);
    }

    public E getLast() {
        return get(size -1);
    }

    public E getFirst() {
        return get(0);
    }

    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append(String.format("Array: size = %d , capacity = %d\n", size, data.length));
        sb.append('[');
        for (int i = 0; i < size; i++) {
            sb.append(data[i]);
            if (i != size - 1)
                sb.append(", ");
        }
        sb.append(']');
        return sb.toString();
    }
}
